Compounds providing a photographic reagent which is originally immobile, balasted or blocked at the active position include positive working compounds disclosed in Belgian Pat. No. 810,195, U.S. Pat. Nos. 4,199,354, 3,980,479, and 4,139,379, and Japanese Patent Application (OPI) No. 130,927/79. The term "OPI" as used herein indicates an "unexamined published application" These compounds are immobile or photographically inactive but can release a mobable photographically useful group by causing an intramolecular nucleophilic substitution reaction or an intramolecular electron transfer reaction.
The aforesaid compounds having the function as described above provide many advantages. However, it is more preferred to improve the characteristics and possibility of the positive working compounds for further increasing the freedom of the designing and latitude on the preparation and processing of photographic elements. It is far more preferred if it is possible to provide compounds having better stability in photographic elements before and after photographic processing. Also, it is preferred to provide a good means for controlling the release of a photographically useful component.